Lithium ion secondary batteries and the like having a large charge/discharge capacity are broadly used for portable devices using batteries including cell phones. Lithium ion secondary batteries having a large charge/discharge capacity and an excellent efficiency are demanded also in applications such as electric bicycles, electric cars, electric tools and electric power storage.
Various materials and techniques are proposed for improvements in characteristics, particularly improvements in charge/discharge cycle characteristics and storage characteristics over a long period, of lithium ion secondary batteries. As one of the techniques, a nonaqueous electrolyte solution secondary battery using an aprotic electrolyte solution containing a sulfonate ester having at least two sulfonyl groups is proposed.
Patent Literature 1 discloses that the fabrication of a secondary battery using an electrolyte solution containing a cyclic sulfonate ester having at least two sulfonyl groups as an aprotic solvent can improve the charge/discharge efficiency of the secondary battery and can improve the cycle characteristics of the secondary battery.
Patent Literature 2 discloses that the use of an electrolyte solution for a secondary battery containing a chain disulfonate ester as an aprotic solvent and the carrying out of the charge/discharge at a predetermined temperature can provide an excellent lithium ion secondary battery exhibiting excellent storage characteristics, good cycle characteristics, small voltage drop and small volume increase.
On the other hand, carbonaceous negative electrode active materials of lithium ion secondary batteries are roughly divided into two types: amorphous carbon having a low crystallinity and graphite having high crystallinity. Since graphite of these has a high initial reversible capacity, and the electrode density of a sheet electrode can be made high, the graphite is applied to applications requiring a high energy density.